Signal processing apparatus and signal processing method

ABSTRACT

A signal processing apparatus includes: a control section; a signal processing section connected with a plurality of signal processing elements and configured to perform signal processing for enhancing or attenuating an input signal in a specific frequency band; and a crossfade signal section including a crossfade signal processing element capable of replacing at least one of the signal processing elements, wherein the control section is configured to control any one of the signal processing elements among the plurality of signal processing elements, and the crossfade signal processing element, to crossfade to the crossfade signal processing element having the signal processing element as a new characteristic, to perform processing for replacing any one of the signal processing elements by the crossfade signal processing element, and to perform the processing on remaining signal processing elements of the plurality of signal processing elements in the signal processing section.

BACKGROUND

The present disclosure relates to a signal processing technique forperforming crossfade processing on a plurality of input signals tooutput a selected signal. More particularly, the present disclosurerelates to a signal processing technique for performing crossfadeprocessing on a plurality of signals whose signal characteristic hasbeen changed using a plurality of signal processing elements.

Related techniques have been disclosed in Japanese Unexamined PatentApplication Publication Nos. 2009-302784 and 06-141236.

The disclosures described in the above patent documents relate totechniques for performing crossfade processing on signals.

In an signal processing apparatus in which a signal characteristic ischanged by a combination of a plurality of signal processing elements,if a characteristic is changed in a state of inputting one input signal(for example, an audio signal) without a break of the signal, it becomesnecessary to perform crossfade processing using a crossfader.

SUMMARY

Incidentally, when a characteristic is changed by crossfade processingusing a crossfader, a same number of signal processing elements as anoriginal number of signal processing elements becomes necessary. That isto say, a double number of resources become necessary. However, thisbecomes difficult to achieve particularly in a situation of limitedresources, by restriction of a circuit size, and by restriction of powerconsumption, etc.

It is desirable to achieve a signal processing apparatus capable ofperforming crossfade processing with as little resource as possible inorder to change a characteristic.

According to an embodiment of the present disclosure, there is provideda signal processing apparatus including: a control section; a signalprocessing section connected with a plurality of signal processingelements and configured to perform signal processing for enhancing orattenuating an input signal in a specific frequency band; and acrossfade signal section including a crossfade signal processing elementcapable of replacing at least one of the signal processing elementsamong the plurality of signal processing elements, wherein the controlsection is configured to control any one of the signal processingelements among the plurality of signal processing elements, and thecrossfade signal processing element in the crossfade signal section, tocrossfade to the crossfade signal processing element having the signalprocessing element as a new characteristic, to perform processing forreplacing any one of the signal processing elements by the crossfadesignal processing element, and to perform the processing on remainingsignal processing elements of the plurality of signal processingelements in the signal processing section.

According to another embodiment of the present disclosure, there isprovided a method of processing a signal to change a characteristic of asignal processing apparatus including a control section, a signalprocessing section connected with a plurality of IIR filters andconfigured to perform signal processing for enhancing or attenuating aninput signal in a specific frequency band, and a crossfade signalsection including a crossfade IIR filter capable of replacing at leastone of the IIR filters among the plurality of IIR filters, the methodincluding: controlling the crossfade IIR filter and changing thecrossfade IIR filter to have a new characteristic; crossfading any oneof the IIR filters among the plurality of IIR filters to the crossfadeIIR filter having the new characteristic; replacing any one of the IIRfilters by the crossfade IIR filter; and enabling to perform thechanging to have a new characteristic, the crossfading, and thereplacing on the plurality of IIR filters.

It is possible to reduce resources, such as signal processing elements,for example, filter elements, etc. Thereby, it is possible to change acharacteristic of an input signal in limited resources. Further, it ispossible to reduce power consumption by reduction in resources.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1G are block diagrams according to a first embodiment;

FIG. 2 is a flowchart according to the first embodiment;

FIGS. 3A-3D are block diagrams according to a second embodiment;

FIG. 4 is a flowchart according to the second embodiment;

FIGS. 5A-5D are block diagrams according to a third embodiment;

FIG. 6 is a flowchart according to the third embodiment;

FIGS. 7A-7D are block diagrams according to a fourth embodiment;

FIGS. 8A-8E are block diagrams according to a fifth embodiment;

FIG. 9 is a flowchart according to the fifth embodiment;

FIGS. 10A-10G are block diagrams according to a sixth embodiment;

FIG. 11 is a diagram illustrating characteristics of a bandpass filterand a characteristic of MPF; and

FIG. 12 is a block diagram of a general signal processing apparatus thatchanges a signal characteristic and causes crossfade.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following, descriptions will be given of embodiments of thepresent disclosure, etc., in the following order. In this regard, in theembodiments, descriptions will be given of cases where a combination ofa plurality of IIR filters is used as filter elements, which are signalprocessing elements, as examples. A filter element is not limited to anIIR filter. A FIR filter may be used.

1. Overview of crossfade processing operation

2. First embodiment

3. Second embodiment

4. Third embodiment

5. Fourth embodiment

6. Fifth embodiment

7. Sixth embodiment

1. Overview of Crossfade Processing Operation

First, descriptions will be given of characteristics of a mid presencefilter (MPF) and a band-pass filter with reference to FIG. 11.

As illustrated on the right in FIG. 11, an MPF has a function ofenhancing or attenuating a characteristic with a predetermined frequency(fc) as center. A band-pass filter has a function of passing only apredetermined frequency (fc), and not passing the other frequencies(attenuating). In an MPF, a bandwidth is variable in the same manner asa band-pass filter. Also, it is possible to change an amount ofamplification or an amount of attenuation.

An equalizer that changes a frequency characteristic of an input signal(for example, audio signal) is formed by connecting MPFs in series.Also, a normal MPF is formed by connecting IIR filters in series.

The present disclosure is an advanced sequence of an IIR filter signalprocessing sequence including the MPF.

A description will be given of an overview of operation for performingcrossfade processing on a signal to change a signal characteristic withreference to FIG. 12.

FIG. 12 illustrates a normal configuration in the case of performingcrossfade processing on a signal to change a signal characteristic.

IIR filters 1, 2, and 3 are filters for performing original signalprocessing. Thereby, as described above, an equalizer is formed. Aninput signal passes through the IIR filters 1, 2, and 3 so that theoriginal signal processing is performed.

IIR filters 61, 62, and 63 are filters for performing new signalprocessing. A signal path is changed so that an input signal passesthrough the IIR filters 61, 62, and 63, and thereby the new signalprocessing is performed.

A change of paths is made such that an input signal (for example, anaudio signal) is not lost. For this purpose, one signal is faded in, andat the same time, the other is faded out. Such a change is calledcrossfade processing. By an amplifier 64, an amplifier 65, and an adder66, crossfade processing is achieved. The amplifiers 64 and 65 arecalled faders. By controlling amplifiers 64 and 65, it is possible tochange the signal path from the path of the IIR filters 1, 2, and 3 tothe path of the IIR filters 61, 62, and 63, and to change thecharacteristic of the signal path without stopping the input signal.

However, in the case of the configuration in FIG. 12, the same number ofIIR filters are necessary as that necessary for performing originalsignal processing, and thus a problem occurs in effective utilization ofhardware.

2. First Embodiment

FIGS. 1A, 1B, 1C, 1D, 1E, 1F, and 1G are block diagrams for explaining afirst embodiment of the present disclosure. These block diagramsrepresent configurations of a signal processing apparatus, and representconnection states of components for individual processing for signalprocessing in FIG. 1A to FIG. 1G.

A signal processing apparatus according to the present embodimentincludes IIR filters 1, 2, and 3, a reserve IIR filter 4, amplifiers 10and 11, an adder 12 and a control section 8.

The signal processing apparatus is assumed to be an equalizer. The IIRfilter 1, 2, and 3 constitute, with respect to an input signal (forexample, an audio signal), for example, an equalizer that performssignal processing for enhancing or attenuating a specific frequency bandsignal. Here, it is assumed that the IIR filters are formed to be inthree stages in series.

The reserve IIR filter 4 is in an unused state, and is used for changinga characteristic of the equalizer.

The amplifiers 10 and 11, and the adder 12 are crossfaders, and are usedfor crossfade processing.

The control section 8 performs connection control of the individualcomponents, and controls the amplifiers 10 and 11, and the adder 12 toperform crossfade processing control.

A description will be given of a processing procedure for changing acharacteristic of an equalizer according to the present embodiment withreference to FIGS. 1A to 1G. In order to change the characteristic, theIIR filters 1, 2, and 3 are subjected to crossfading in sequence one byone.

FIG. 1A illustrates an original state. An input signal is subjected tosignal processing through the IIR filters 1, 2, and 3, and is output.

FIG. 1B is a diagram illustrating a connection in which a characteristicof the IIR filter 1 is changed and crossfading is performed. Acrossfader including a reserve (unused) IIR filter 4, the amplifiers 10,11 and the adder 12 is connected to a stage of the IIR filter 1 asillustrated in FIG. 1B.

At this time, the IIR filter 4 is set to a characteristic B(1) to bechanged. The original characteristic of the IIR filter 1 is A(1). Next,the crossfader performs crossfading from the IIR filter 1 to the IIRfilter 4. After crossfading is complete, the invalidated IIR filter 1and the crossfader that has completed crossfading are cut off, and thebuffer of the IIR filter 1 is cleared. That is to say, thecharacteristic of the IIR filter 1, A(1), is cleared and changed toreserve (unused). Thereby, it is possible to replace the IIR filter 1having the characteristic A(1) by the IIR filter 4 having thecharacteristic B(1).

FIG. 1C is a diagram after the IIR filter 1 has been replaced by the IIRfilter 4. The IIR filter 1 becomes reserved (unused).

FIG. 1D is a diagram illustrating a connection in which a characteristicof the IIR filter 2 is changed and crossfading is performed. Acrossfader including a reserve (unused) IIR filter 1 and the amplifiers10, 11 and the adder 12 are connected to a stage of the IIR filter 2 asillustrated in FIG. 1D.

At this time, the IIR filter 1 is set to a characteristic B(2) to bechanged. The original characteristic of the IIR filter 2 is A(2). Next,the crossfader performs crossfading from the IIR filter 2 to the IIRfilter 1. After the crossfading is complete, the invalidated IIR filter2 and the crossfader that has completed crossfading are cut off, and thebuffer of the IIR filter 2 is cleared. That is to say, thecharacteristic of the IIR filter 2, A(2), is cleared and reserved(unused). Thereby, it is possible to replace the IIR filter 2 having thecharacteristic A(2) by the IIR filter 1 having the characteristic B(2).

FIG. 1E is a diagram after the IIR filter 2 has been replaced by the IIRfilter 1. The IIR filter 2 becomes reserved (unused).

FIG. 1F is a diagram illustrating a connection in which a characteristicof the IIR filter 3 is changed and crossfading is performed. Acrossfader including a reserve (unused) IIR filter 2 and the amplifiers10, 11 and the adder 12 are connected to a stage of the IIR filter 3 asillustrated in FIG. 1F.

At this time, the IIR filter 2 is set to a characteristic B(3) to bechanged. The original characteristic of the IIR filter 3 is A(3). Next,the crossfader performs crossfading from the IIR filter 3 to the IIRfilter 2. After crossfading is complete, the invalidated IIR filter 3and the crossfader that has completed crossfading are cut off, and thebuffer of the IIR filter 3 is cleared. That is to say, thecharacteristic of the IIR filter 3, A(3), is cleared and reserved(unused). Thereby, it is possible to replace the IIR filter 3 having thecharacteristic A(3) by the IIR filter 2 having the characteristic B(3).

FIG. 1G is a diagram after the IIR filter 3 has been replaced by the IIRfilter 2. The IIR filter 3 becomes reserved (unused).

By the above processing, the IIR filter 1 having the characteristicA(1), the IIR filter 2 having the characteristic A(2), and the IIRfilter 3 having the characteristic A(3), which are included in theequalizer, are replaced by the IIR filter 4 having the characteristicB(1), the IIR filter 1 having the characteristic B(2), and the IIRfilter 2 having the characteristic B(3), respectively, and thus thecharacteristic of the equalizer can be changed.

In this case, it is sufficient to have one IIR filter in order to changethe characteristic. Compared with the method described with reference toFIG. 12, it is possible to drastically reduce the number of IIR filters,that is to say, to save hardware resources. Also, the number of IIRfilters is reduced, and thus it becomes possible to save power.

However, overall processing time is increased by the number ofcrossfaders compared with the case in FIG. 12, but a processing speedper unit time is increased, and thus it causes no problem.

FIG. 2 is a flowchart according to a first embodiment of the presentdisclosure. The above-described procedure is expressed in a form of aflowchart.

The above-described procedure will be described with reference to FIG.2.

In step S101, the control section 8 sets X to 0. That is to say, thecontrol section 8 clears X.

In step S102, the control section 8 counts up X. An initial value of Xis 1.

In step S103, the control section 8 sets a reserve IIR filter 4, that isto say, an unused IIR filter 4 to have a characteristic of B(1).

In step S104, the control section 8 crossfades the IIR filter 1 havingA(1) to the IIR filter 4 having B(1).

In step S105, the control section 8 changes the IIR filter 1 to reserve(unused).

In step S106, the control section 8 cuts off the crossfader includingthe IIR filter 3, the amplifiers 10, 11, and the adder 12.

In step S107, the control section 8 determines whether X exceeds 3 ornot. If X does not exceed 3, the processing from step S102 to step S106is repeated until X becomes 3. If X exceeds 3, the processing isterminated.

By this processing, it is possible to replace the IIR filter 1 havingthe characteristic A(1), the IIR filter 2 having the characteristic A(2)and the IIR filter 3 having the characteristic A(3) by the IIR filter 4having characteristic B(1), the IIR filter 1 having the characteristicB(2) and the IIR filter 2 having the characteristic B(3).

3. Second Embodiment

FIGS. 3A, 3B, 3C, and 3D are block diagrams for explaining a secondembodiment of the present disclosure. The same reference letters aregiven to the same parts as those already described, and descriptionsthereof will be omitted. These block diagrams represent configurationsof a signal processing apparatus, and represent connection states ofcomponents for each processing for performing signal processing in FIG.3A to FIG. 3D in the same manner as FIGS. 1A to 1G.

A signal processing apparatus according to the present embodimentincludes IIR filters 1, 2, 3 and 7, reserve IIR filters 5, 6, amplifiers10, 11, an adder 12 and a control section 8.

The signal processing apparatus is assumed to be an equalizer. The IIRfilters 1, 2, 3 and 7 constitute, with respect to an input signal (forexample, an audio signal), for example, an equalizer. Here, it isassumed that the IIR filters are formed to be in four stages in series.

The reserve IIR filters 5, 6 are in an unused state, and are used forchanging a characteristic of the equalizer.

The amplifiers 10, 11, and the adder 12 are crossfaders, and are usedfor crossfade processing.

The control section 8 performs connection control of the individualcomponents, and controls the amplifiers 10, 11, and the adder 12 toperform crossfade processing control.

In the present embodiment, the number of reserve (unused) IIR filters isadded so that processing speed is aimed to be improved. In the presentembodiment, one reserve (unused) IIR filter is added, and the filtersare assumed to be IIR filters 5, 6.

A description will be given of a processing procedure for changing acharacteristic of an equalizer according to the present embodiment withreference to FIGS. 3A to 3D. In order to change the characteristic, theIIR filters 1, 2 and the IIR filters 3, 7 are subjected to crossfadingindividually in sequence.

FIG. 3A illustrates a state before the change. An input signal issubjected to signal processing through the IIR filters 1, 2, 3 and 7,and is output.

FIG. 3B is a diagram illustrating a connection in which characteristicsof the IIR filters 1, 2 are changed and crossfading is performed. Acrossfader including a reserve (unused) IIR filters 5, 6, the amplifiers10, 11, and the adder 12 is connected to a stage of the IIR filters 1, 2as illustrated in FIG. 3B.

At this time, the IIR filters 5, 6 are set to the characteristic B(1),B(2) to be changed, respectively. The original characteristics of theIIR filters 1, 2 are A(1), A(2), respectively. Next, the crossfaderperforms crossfading from the IIR filters 1, 2 to the IIR filters 5, 6.After the crossfading is complete, the invalidated IIR filters 1, 2 andthe crossfader that has completed crossfading are cut off, and thebuffers of the IIR filters 1, 2 are cleared. That is to say, A(1), A(2),which are characteristics of the IIR filter 1, 2, respectively, arecleared and changed to unused. That is to say, the characteristics arechanged to reserved.

Thereby, it is possible to replace the IIR filters 1, 2 having thecharacteristic A(1), A(2) by the IIR filters 5, 6 having thecharacteristic B(1), B(2), respectively.

FIG. 3C is a diagram illustrating a connection in which characteristicsof the IIR filters 3, 7 are changed and crossfading is performed. Acrossfader including a reserve (unused) IIR filters 1, 2, the amplifiers10, 11, and the adder 12 is connected to a stage of the IIR filter 3, 7as illustrated in FIG. 3C.

At this time, the IIR filters 1, 2, which have become reserved (unused)in FIG. 3B, are set to have the characteristics B(3), B(4),respectively, to which changes are made. The original characteristics ofthe IIR filters 3, 7 are A(3), A(4), respectively. Next, the crossfaderperforms crossfading from the IIR filters 3, 7 to the IIR filters 1, 2,respectively. After the crossfading is complete, the invalidated IIRfilters 3, 7 and the crossfader that has completed crossfading are cutoff, and the buffers of the IIR filters 3, 7 are cleared. That is tosay, A(3) and A(4), which are characteristics of the IIR filters 3, 7,are cleared and are set to unused. That is to say, the characteristicsare reserved.

Thereby, it is possible to replace the IIR filter 3, 7 having thecharacteristic A(3), A(4) by the IIR filter 1, 2 having thecharacteristic B(3), B(4), respectively.

FIG. 3D is a diagram after the IIR filter 3 and the IIR filter 7 havebeen replaced by the IIR filter 1 and the IIR filter 2. The IIR filter 3and the IIR filter 7 become reserved, and thus unused.

By the above processing, the IIR filter 1 having the characteristicA(1), the IIR filter 2 having the characteristic A(2), the IIR filter 3having the characteristic A(3), and the IIR filter 4 having thecharacteristic A(4), which are included in the equalizer, are replacedby the IIR filter 5 having the characteristic B(1), the IIR filter 6having the characteristic B(2), the IIR filter 1 having thecharacteristic B(3), and the IIR filter 2 having the characteristicB(4), respectively, and thus the characteristic of the equalizer can bechanged.

In this case, the number of IIR filters for changing characteristics istwo, and thus it is possible to complete overall processing at a speedtwo times the speed of the method described with reference to FIGS. 1Ato 1G.

In the case where 100 IIR filters are used in a signal processingsequence of the equalizer, if 50 IIR filters are provided, it ispossible to complete the entire transition by processing for two times,and thus it is possible to drastically increase the speed. At the sametime, it becomes possible to reduce resources of 50 IIR filters.

FIG. 4 is a flowchart according to the second embodiment of the presentdisclosure. The above-described procedure is expressed in a form of aflowchart.

The above-described procedure will be described with reference to FIG.4.

In step S201, the control section 8 sets X to 0. That is to say, thecontrol section 8 clears X.

In step S202, the control section 8 counts up X by two. An initial valueof X is 2.

In step S203, the control section 8 sets unused IIR filters 5, 6, thatis to say, two reserved IIR filters 5, 6 to have characteristics ofB(1), B(2), respectively.

In step S204, the control section 8 crossfades the IIR filter 1 havingA(1) and the IIR filter 2 having the A(2) to the IIR filter 5 havingB(1) and the IIR filter 6 having B(2), respectively.

In step S205, the control section 8 changes the IIR filter 1 and the IIRfilter 2 to reserved (unused).

In step S206, the control section 8 cuts off the crossfader includingthe reserved (unused) IIR filter 1 and IIR filter 2, and the amplifiers10, 11, and the adder 12.

In step S207, the control section 8 checks whether X exceeds 4 or not.If X does not exceed 4, processing from step S202 to step S206 isrepeated until X becomes 4.

By this processing, it is possible to replace the IIR filter 1 havingthe characteristic A(1), the IIR filter 2 having the characteristicA(2), the IIR filter 3 having the characteristic A(3), and the IIRfilter 7 having the characteristic A(4) by the IIR filter 5 having thecharacteristic B(1), the IIR filter 6 having the characteristic B(2),the IIR filter 1 having the characteristic B(3), and the IIR filter 2having the characteristic B(4).

4. Third Embodiment

FIGS. 5A, 5B, 5C, and 5D are block diagrams for explaining a thirdembodiment of the present disclosure. The same reference letters aregiven to the same parts as those already described, and descriptionsthereof will be omitted. These block diagrams represent configurationsof a signal processing apparatus, and represent connection states ofcomponents for each processing for performing signal processing in FIG.5A to FIG. 5D in the same manner as FIGS. 1A to 1G.

A signal processing apparatus according to the present embodimentincludes IIR filters 1, 2, 3 and 7, reserve IIR filters 5, 6, amplifiers10, 11, an adder 12 and a control section 8.

The signal processing apparatus is assumed to be an equalizer. The IIRfilters 1, 2, 3 and 7 constitute, with respect to an input signal (forexample, an audio signal), for example, an equalizer. Here, it isassumed that the IIR filters are formed to be in four stages in series.

The reserve IIR filters 5, 6 are in an unused state, and are used forchanging a characteristic of the equalizer. In this case, it is possibleto use as reserve IIR filters by changing the number of the reserve IIRfilters.

The amplifiers 10, 11, and the adder 12 are crossfaders, and are usedfor crossfade processing.

The control section 8 performs connection control of the individualcomponents, and controls the amplifiers 10, 11, and the adder 12 toperform crossfade processing control.

In the present embodiment, the number of reserve (unused) IIR filters isadded so that processing speed is aimed to be improved in the samemanner as the second embodiment. In the present embodiment, one reserve(unused) IIR filter is added, and two IIR filters 5, 6 are provided.However, it is possible to apply the two IIR filters together or toapply only one of the two.

A description will be given of a processing procedure for changing acharacteristic of an equalizer according to the present embodiment withreference to FIGS. 5A to 5D. Here, it is assumed that the characteristicof the IIR filter 1 is not changed. It is assumed that thecharacteristics of the IIR filter 2, the IIR filter 3 and the IIR filter7 are to be changed.

FIG. 5A illustrates a state before a change. An input signal issubjected to signal processing through the IIR filters 1, 2, 3 and 7,and is output.

FIG. 5B is a diagram illustrating a connection in which thecharacteristics of the IIR filter 2, 3 are changed and crossfading isperformed. A crossfader including the reserve (unused) IIR filters 5, 6,the amplifiers 10, 11 and the adder 12 is connected to stages of the IIRfilters 2, 3 as illustrated in FIG. 5B.

At this time, the IIR filters 5, 6 are set to characteristic B(2), B(3),to which changes are made, respectively. The original characteristics ofthe IIR filter 2, 3 are A(2), A(3), respectively. Next, the crossfaderperforms crossfading from the IIR filters 2, 3 to the IIR filters 5, 6,respectively. After crossfading is complete, the invalidated IIR filter2, 3 and the crossfader that has completed crossfading are cut off, andthe buffers of the IIR filters 2, 3 are cleared. That is to say, A(2),A(3), which are the characteristics of the IIR filters 2, 3,respectively, are cleared and changed to unused. That is to say, thecharacteristics are changed to reserved.

Thereby, it is possible to replace the IIR filter 2, 3 having thecharacteristic A(2), A(3) by the IIR filter 5, 6 having thecharacteristic B(2), B(3), respectively.

FIG. 5C is a diagram illustrating a connection in which a characteristicof the IIR filter 7 is changed and crossfading is performed. Acrossfader including the reserve (unused) IIR filters 1, 2, theamplifiers 10, 11 and the adder 12 is connected to a stage of the IIRfilter 7 as illustrated in FIG. 5C. It is not necessary to use tworeserve (unused) IIR filters without fail as in the case of the secondembodiment, and it is possible to perform crossfading using only onereserve (unused) IIR filter.

At this time, the IIR filter 2, which has become reserved (unused) inFIG. 5B, is set to the characteristics B(4). The originalcharacteristics of the IIR filter 7 is A(4). Next, the crossfaderperforms crossfading from the IIR filter 7 to the IIR filter 2. Afterthe crossfading is complete, the invalidated IIR filter 7 and thecrossfader that has completed crossfading are cut off, and the buffer ofthe IIR filter 7 is cleared. That is to say, A(4), which is thecharacteristic of the IIR filter 7 is cleared and is set to unused. Thatis to say, the characteristics is reserved.

Thereby, it is possible to replace the IIR filters 3, 7 having thecharacteristics A(3), A(4) by the IIR filter 1, 2 having thecharacteristics B(3), B(4), respectively.

FIG. 5D is a diagram after IIR filters 2, 3 and 7 have been replaced bythe IIR filters 5, 6 and 2, respectively. The IIR filters 3, 7 becomereserved (unused).

By the above processing, the IIR filter 2 having the characteristicA(2), the IIR filter 3 having the characteristic A(3), the IIR filter 7having the characteristic A(3), which are included in the equalizer, arereplaced by the IIR filter 5 having the characteristic B(2), the IIRfilter 6 having the characteristic B(3), the IIR filter 2 having thecharacteristic B(4), respectively, and thus the characteristic of theequalizer can be changed.

In this case, it is possible to set the number of IIR filters forchanging the characteristics to two or one. It is possible to increasethe processing speed compared with the method described with referenceto FIGS. 1A to 1G.

FIG. 6 is a flowchart according to the third embodiment of the presentdisclosure. The above-described procedure is expressed in a form of aflowchart.

The above-described procedure will be described with reference to FIG.6.

In step S301, control section 8 sets X to 0. That is to say, the controlsection 8 clears X.

In step S302, the control section 8 counts up X by two. An initial valueof X is 2.

In step S303, the control section 8 determines whether to change thecharacteristic of the IIR filter 1. If the characteristic of the IIRfilter 1 is not changed, the processing proceeds to step S304. Here, thecharacteristic of the IIR filter 1 is not changed and the processingproceeds to step S304.

In step S304, the control section 8 counts down X by 1. X becomes 1. Nis not greater than 4, and thus the processing proceeds to step S302after determination in step S309. X is counted up by 2, and thus Xbecomes 3. The processing proceeds to step S303. In 5303, the controlsection 8 determines whether to change the characteristic of the IIRfilter 2 or not. The IIR filter 2 is changed, and thus the processingproceeds to step S305.

In step S305, the control section 8 determines whether to change thecharacteristic of the IIR filter 3 or not. The IIR filter 3 is changed,and thus the processing proceeds to step S306.

In step S306, the control section 8 sets two reserve (unused) IIRfilters 5 and 6 to have the characteristics of B(2) and B(3),respectively.

In step S307, the control section 8 crossfades the IIR filter 2 havingA(2) and the IIR filter 3 having the A(3) to the IIR filter 5 having theB(2) and the IIR filter 6 having the B(3), respectively. And the IIRfilter 2 and the IIR filter 3 become reserved (unused).

In step S308, the control section 8 cuts off the crossfader includingthe reserved (unused) IIR filter 2 and IIR filter 3, the amplifiers 10,11 and the adder 12. Next, the processing proceeds to step S309.

In the determination in step S309, X is 3 and is not greater than 4.Thus the processing proceeds to step S302, and the control section 8counts up X by two. X becomes 5. The IIR filter 7 having thecharacteristic A(4) is changed, the IIR filter having A(5) is notchanged (existent), and thus the processing proceeds to step S310.

In step S310, the control section 8 sets one reserved (unused) IIRfilter to have the characteristic of B(4).

In step S311, the control section 8 crossfades the IIR filter 7 havingA(4) to the IIR filter 2 having B(4). And the control section 8 changesthe IIR filter 7 to reserved (unused).

In step S308, the control section 8 cuts off the crossfader includingthe reserved IIR filter 7 and IIR filter 3, the amplifiers 10, 11 andthe adder 12.

The processing proceeds to step S309. X is greater than 4, and thus theprocessing is terminated.

Here, a description has been given of the case where N is 4. However,the same processing is performed in the case where N is an any value.

By this processing, it is possible to replace the IIR filter 2 havingthe characteristic A(2), the IIR filter 3 having the characteristicA(3), and the IIR filter 7 having the characteristic A(4) by the IIRfilter 5 having the characteristic B(2), the IIR filter 6 having thecharacteristic B(3), and the IIR filter 2 having the characteristicB(4), respectively, with keeping the characteristic of the IIR filter 1as it is.

5. Fourth Embodiment

FIGS. 7A, 7B, 7C, and 7D are block diagrams for explaining a fourthembodiment of the present disclosure. The same reference letters aregiven to the same parts as those already described, and descriptionsthereof will be omitted. These block diagrams represent configurationsof a signal processing apparatus, and represent connection states ofcomponents for each processing for performing signal processing in FIG.7A to FIG. 7D in the same manner as FIGS. 1A to 1G.

A signal processing apparatus according to the present embodimentincludes IIR filters 1, 2, 3, a reserve IIR filter 4, amplifiers 21, 22,23, 24, adders 25, 26, 27, and a control section 8. The amplifier 21 andthe adder 25 are connected to the IIR filter 1. In the same manner, theamplifier 22, the adder 26, and the amplifier 23, the adder 23 areconnected to the IIR filters 2, 3, respectively. The reserve IIR filter4 and the amplifier 24 are provided for crossfade processing.

The signal processing apparatus is assumed to be an equalizer. The IIRfilters 1, 2, and 3 constitute, with respect to an input signal (forexample, an audio signal), for example, an equalizer. Here, it isassumed that the IIR filters are formed in three stages in series.

The reserve IIR filter 4 is in an unused state, and is used for changinga characteristic of the equalizer.

The control section 8 performs connection control of the individualcomponents, and controls the amplifiers 21, 22, 23, 24, and the adders25, 26, 27 to perform crossfade processing control.

In the present embodiment, an amplifier and an adder are connected toeach IIR filter included in the equalizer whose characteristic has notbeen changed yet. As components for performing crossfade, reserve(unused) IIR filter and amplifier are provided. Thereby, it is possibleto achieve the same function as that of the first embodiment.

A description will be given of a processing procedure for changing acharacteristic of an equalizer according to the present embodiment withreference to FIGS. 7A to 7D. In order to change the characteristic, theIIR filters 1, 2, 3 are subjected to crossfading in sequence one by oncein order to change characteristics.

FIG. 7A illustrates an original state. An input signal is subjected tosignal processing through the IIR filters 1, 2, 3, and is output. Aninput signal goes through the IIR filters 1, 2 and 3 so as to besubjected to the signal processing, and is output. An amplifier and anadder are connected to each IIR filter, but the gain of the amplifierought to be set to 1, and an input terminal of the adder, to whichnothing is connected, ought to be in a no-signal state (0).

FIG. 7B is a diagram illustrating a connection in which a characteristicof the IIR filter 1 is changed and crossfading is performed. The reserve(unused) IIR filter 4, the amplifier 24, and the adder 12 are connectedto a stage of the amplifier 21 and the adder 25 that are additionallyconnected to the IIR filter 1 as illustrated in FIG. 7B.

At this time, the IIR filter 4 is set to the characteristic B(1), towhich a change is made. The original characteristic of the IIR filter 1is A(1). Next, the crossfader including a connection of the IIR filter4, the amplifier 24, the amplifier 21, and the adder 25 performscrossfading from the IIR filter 1 to the IIR filter 4. After crossfadingis complete, the invalidated IIR filter 1 and the amplifier 21 connectedthereto are cut off, and at the same time, an input terminal that hasbeen connected to the amplifier 21 of the adder 25 is changed to ano-signal state (0). The buffer of the IIR filter 1 is cleared. That isto say, A(1), which is characteristic of the IIR filter 1 is cleared andchanged to reserved (unused). Thereby, it is possible to replace the IIRfilter 1 having the characteristic A(1) by the IIR filter 4 having thecharacteristic B(1).

FIG. 7C is a diagram illustrating a connection in which the IIR filter 1having the characteristic A(1) is replaced by the IIR filter 4 havingthe characteristic B(1), the IIR filter 2 having the characteristic A(2)is replaced by the IIR filter 1 having the characteristic B(2), and atthe same time, the characteristic of the IIR filter 3 is changed andcrossfading is performed.

The reserved (unused) IIR filter 1 and the amplifier 21 are additionallyconnected to a stage in which the amplifier 22 and the adder 26 areconnected to the IIR filter 2.

At this time, the IIR filters 1, which has been reserved (unused) is setto the characteristics B(2), to which a change is made. In the samemanner as in the case of FIG. 7B, crossfading is performed from the IIRfilter 2 to the IIR filters 1. After crossfading is complete, theinvalidated IIR filter 2 and the amplifier 21 connected thereto are cutoff, and at the same time, an input terminal that has been connected tothe amplifier 21 of the adder 26 is changed to a no-signal state (0).The buffer of the IIR filter 2 is cleared. That is to say, A(2), whichis the characteristic of the IIR filter 2 is cleared and changed toreserved (unused). Thereby, it is possible to replace the IIR filter 2having the characteristic A(2) by the IIR filter 1 having thecharacteristic B(2).

FIG. 7D is a diagram illustrating a connection in which the IIR filter 1having the characteristic A(1) is replaced by the IIR filter 4 havingthe characteristic B(1), further the IIR filter 2 having thecharacteristic A(2) is replaced by the IIR filter 1 having thecharacteristic B(2), and at the same time, the characteristic of the IIRfilter 3 is changed and crossfading is performed.

The reserved (unused) IIR filter 2 and the amplifier 22 are additionallyconnected to a stage in which the amplifier 23 and the adder 27 areconnected to the IIR filter 3.

At this time, the IIR filters 2, which has been reserved (unused) is setto the characteristics B(3), to which a change is made. In the samemanner as in the case of FIG. 7C, crossfading is performed from the IIRfilter 3 to the IIR filters 2. After crossfading is complete, theinvalidated IIR filter 3 and the amplifier 23 connected thereto are cutoff, and at the same time, an input terminal that has been connected tothe amplifier 23 of the adder 27 is changed to a no-signal state (0).The buffer of the IIR filter 3 is cleared. That is to say, A(3), whichis the characteristic of the IIR filter 3 is cleared and changed toreserved (unused). Thereby, it is possible to replace the IIR filter 3having the characteristic A(3) by the IIR filter 2 having thecharacteristic B(3).

By the above processing, the IIR filter 1 having the characteristicA(1), the IIR filter 2 having the characteristic A(2), the IIR filter 3having the characteristic A(3), which are included in the equalizer, arereplaced by the IIR filter 4 having the characteristic B(1), the IIRfilter 1 having the characteristic B(2), the IIR filter 2 having thecharacteristic B(3), respectively, and thus the characteristic of theequalizer can be changed.

In the present embodiment, amplifiers and adders are connected to aplurality of original IIR filters, respectively, and further, anamplifier is connected to the reserved (unused) IIR filter. Accordingly,the processing flow thereof is the same as that of the first embodiment.Accordingly, a description thereof will be omitted.

6. Fifth Embodiment

FIGS. 8A, 8B, 8C, 8D and 8E are block diagrams for explaining a fifthembodiment of the present disclosure. The same reference letters aregiven to the same parts as that already described, and descriptions willbe omitted. These block diagrams represent configurations of a signalprocessing apparatus, and represent connection states of components forindividual processing for signal processing as illustrated in FIG. 8A toFIG. 8E.

A signal processing apparatus according to the present embodimentincludes IIR filters 1, 2, 3, a reserve IIR filter 4, amplifiers 31, 32,33, 34, 35, 36, 37, 38, an adders 41, 42, 43, 44, and a control section8. The amplifier 31, 33, and 35 are connected to output sides of the IIRfilter 1, 2 and 3, respectively. Further, amplifiers 32, 34 and 36 areprovided so as to bypass the IIR filter 1 and the amplifier 31, the IIRfilter 2 and the amplifier 33, and the IIR filter 3 and the amplifier35, respectively.

An output of the amplifier 31 and an output of the amplifier 32 areconnected to the adder 41, and an output of the adder 41 is connected toan input of the IIR filter 2. An output of the amplifier 33 and anoutput of the amplifier 34 are connected to the adder 42, and an outputof the adder 42 is connected to an input of the IIR filter 3. An outputof the amplifier 35 and an output of the amplifier 36 are connected tothe adder 43. An output of the adder 43 is connected to an input of thereserve IIR filter 4.

Also, an amplifier 37 is connected to an output side of the reserve IIRfilter 4 for performing the above-described crossfade, an amplifier 38is disposed to bypass the reserve IIR filter 4 and the amplifier 37, andan output of the amplifier 37 and an output of the amplifier 38 areconnected to the adder 44.

The signal processing apparatus according to the present embodiment isassumed to be an equalizer. The IIR filters 1, 2, and 3 constitute, withrespect to an input signal (for example, an audio signal), for example,an equalizer. Here, it is assumed that the IIR filters are formed inthree stages in series.

The reserve IIR filter 4 is in an unused state, and is used for changinga characteristic of the equalizer.

The control section 8 performs connection control of the individualcomponents, and controls the amplifiers 31, 32, 33, 34, 35, 36, 37 and38 to perform crossfade processing control.

In the present embodiment, an amplifier and an adder are connected toeach IIR filter included in an equalizer whose characteristic has notbeen changed yet. As components for performing crossfade, the reserved(unused) IIR filter 4 is connected in series so that the totalcharacteristic is changed.

A description will be given of a processing procedure for changing acharacteristic of an equalizer according to the present embodiment withreference to FIGS. 8A to 8E. In order to change the characteristic, theIIR filters 1, 2 and 3 are subjected to crossfading in sequence one byonce in order to change the characteristics.

FIG. 8A illustrates an original state. An input signal goes through theIIR filters 1, 2 and 3, and is subjected to signal processing. In thiscase, gains of the amplifiers 31, 33, 35 and 38 are set to 1. Outputsignals of the amplifier 32, 34, 36 and 37 are set to a no-signal state(gain 0). Thereby, the input signal goes through the IIR filters 1, 2and 3, and bypasses the reserve IIR filter 4 to be output.

FIG. 8B is a diagram illustrating a connection state in which acharacteristic of the IIR filter 1 is changed and crossfading isperformed. First, the characteristic of the reserve IIR filter 4 is setto characteristic B(1), to which a change is made.

The amplifier 37 is changed from a state having no output signal (gain0) to a state having an output signal (gain 1). The amplifier 38 ischanged from a state having an output signal (gain 1) to a state havingno output signal (gain 0). At the same time, the amplifier 31 is changedfrom a state having an output signal (gain 1) to a state having nooutput signal (gain 0), and the amplifier 32 is changed from a statehaving no output signal (gain 0) to a state having an output signal(gain 1). Thereby, the output signal of the IIR filter 1 is crossfadedto the output signal of the IIR filter 4, and the IIR filter 1 havingthe characteristic A(1) is replaced by the IIR filter 4 having thecharacteristic B(1).

FIG. 8C is a diagram illustrating a state in which the buffer of the IIRfilter 1 is cleared so that the characteristic A(1) is cleared, and ischanged to reserved (unused).

FIG. 8D is a diagram illustrating a connection state in which thecharacteristic of the IIR filter 2 is changed to perform crossfading.First, the characteristic of the reserve IIR filter 1 is set tocharacteristic B(2), to which a change is made.

The amplifier 31 is changed from a state having no output signal (gain0) to a state having an output signal (gain 1). The amplifier 32 ischanged from a state having an output signal (gain 1) to a state havingno output signal (gain 0). At the same time, the amplifier 33 is changedfrom a state having an output signal (gain 1) to a state having nooutput signal (gain 0), and the amplifier 34 is changed from a statehaving no output signal (gain 0) to a state having an output signal(gain 1). Thereby, the output signal of the IIR filter 2 is crossfadedto the output signal of the IIR filter 1, and the IIR filter 2 havingthe characteristic A(2) is replaced by the IIR filter 1 having thecharacteristic B(2).

FIG. 8E is a diagram illustrating a state in which the buffer of the IIRfilter 2 is cleared so that the characteristic A(2) is cleared, and thefilter is changed to reserved (unused).

The IIR filter 3 is also connected and controlled in the same manner asillustrated in FIG. 8B, FIG. 8C or FIG. 8D, FIG. 8E so that the outputof the IIR filter 3 having the characteristic A(3) is crossfaded to theoutput of the IIR filter 2 having the characteristic B(3), and thus itis possible to replace the IIR filter 3 having the characteristic A(3)by the IIR filter 2 having the characteristic B(3).

FIG. 9 is a flowchart according to a fifth embodiment of the presentdisclosure. The above-described procedure is expressed in a form of aflowchart.

The above-described procedure will be described with reference to FIG.9.

In step S401, the control section 8 sets X to 0. That is to say, thecontrol section 8 clears X.

In step S402, the control section 8 counts up X. An initial value of Xis 1.

In step S403, the control section 8 sets a reserve IIR filter 4 to havethe characteristic of B(1).

In step S404, the control section 8 crossfades the output of the IIRfilter 1 having A(1) to the output of the IIR filter 4 having B(1).

In step S405, the control section 8 changes the IIR filter 1 to reserved(unused).

In step S406, the control section 8 checks whether X is greater than 4or not. If not greater than 4, the processing from step S402 to stepS406 is repeated until X becomes 4.

By the above processing, it is possible to change the characteristic ofthe equalizer.

7. Sixth Embodiment

FIGS. 10A, 10B, 10C, 10D, 10E, 10F and 10G are block diagrams forexplaining a sixth embodiment of the present disclosure. The samereference letters are given to the same parts as that already described,and descriptions thereof will be omitted. These block diagrams representconfigurations of a signal processing apparatus, and representconnection states of components for each processing for performingsignal processing as illustrated in FIG. 10A to FIG. 10G.

A signal processing apparatus according to the present embodimentincludes IIR filters 1, 2, 3, a reserve IIR filter 4, amplifiers 51, 52,53, 54, an adder 45, and a control section 8. The amplifier 52, 53 and54 are connected to output sides of the IIR filter 1, 2 and 3,respectively.

The amplifier 51 is connected to the output side of the reserve IIRfilter for performing crossfading. Further, outputs of the amplifiers52, 53, 54, and 51 are connected to the adder 45.

A signal processing apparatus according to the present embodiment is thecase where the IIR filters 1, 2 and 3 are connected in parallel.Further, in order to perform crossfading, four reserve IIR filters 4 areconnected in parallel so that the characteristic of the signalprocessing apparatus is changed. The control section 8 performsconnection control of each component, and performs control of theamplifiers 52, 53, 54 and 51, and crossfade processing control.

A description will be given of a processing procedure for changing acharacteristic of a signal processing apparatus according to the presentembodiment with reference to FIGS. 10A to 10G. In order to change thecharacteristic, the IIR filters 1, 2 and 3 are subjected to crossfadingin sequence one by once in order to change the characteristic.

FIG. 10A illustrates an original state. An input signal is received andsubjected to signal processing by each of the IIR filters 1, 2, and 3,and a combined output thereof is output. In this case, the amplifiers52, 53 and 54 are set to a state having output (gain 1), and theamplifier 51 is set to a state having no (gain 0).

FIG. 10B is a diagram illustrating a connection state in which acharacteristic of the IIR filter 1 is changed and crossfading isperformed. First, the characteristic of the reserve IIR filter 4 is setto the characteristic B(1), to which a change is made.

The amplifier 51 is changed from a state having no output signal (gain0) to a state having an output signal (gain 1). At the same time, theamplifier 52 is changed from a state having an output signal (gain 1) toa state having no output signal (gain 0). Thereby, the output signal ofthe IIR filter 1 is crossfaded to the output signal of the IIR filter 4,and the IIR filter 1 having the characteristic A(1) is replaced by theIIR filter 4 having the characteristic B(1).

FIG. 10C is a diagram illustrating a state in which the buffer of theIIR filter 1 is cleared so that the characteristic A(1) is cleared, andis changed to reserved (unused).

FIG. 10D is a diagram illustrating a connection state in which thecharacteristic of the IIR filter 2 is changed to perform crossfading.First, the characteristic of the reserve IIR filter 1 is set to thecharacteristic B(2), to which a change is made.

The amplifier 52 is changed from a state having no output signal (gain0) to a state having an output signal (gain 1). The amplifier 53 ischanged from a state having an output signal (gain 1) to a state havingno output signal (gain 0). Thereby, the output signal of the IIR filter2 is crossfaded to the output signal of the IIR filter 1, and the IIRfilter 2 having the characteristic A(2) is replaced by the IIR filter 1having the characteristic B(2).

FIG. 10E is a diagram illustrating a state in which the buffer of theIIR filter 2 is cleared so that the characteristic A(2) is cleared, andthe filter is changed to reserved (unused).

FIG. 10F is a connection state in which the characteristic of the IIRfilter 3 is changed, and crossfading is performed. First, thecharacteristic of the reserve IIR filter 2 is changed to thecharacteristic B(3), to which a change is made.

The amplifier 53 is changed from a state having no output signal (gain0) to a state having an output signal (gain 1). At the same time, theamplifier 54 is changed from a state having an output signal (gain 1) toa state having no output signal (gain 0). Thereby, the output signal ofthe IIR filter 3 is crossfaded to the output signal of the IIR filter 2,and the IIR filter 3 having the characteristic A(3) is replaced by theIIR filter 2 having the characteristic B(3).

FIG. 10G illustrates a state in which all the characteristics of thesignal processing apparatus have been changed. The buffer of the IIRfilter 3 is cleared, and finally, the IIR filter 3 is changed toreserved (unused).

The processing flow thereof is different from that of the firstembodiment only in that the IIR filters are connected in parallel, andbasically the same as that of the first embodiment. Accordingly, adescription of the processing flow will be omitted.

In this regard, the present technique can also be configured as follows.

(1) A signal processing apparatus including:

a control section;

a signal processing section connected with a plurality of signalprocessing elements and configured to perform signal processing forenhancing or attenuating an input signal in a specific frequency band;and

a crossfade signal section including a crossfade signal processingelement capable of replacing at least one of the signal processingelements among the plurality of signal processing elements,

wherein the control section is configured to control any one of thesignal processing elements among the plurality of signal processingelements, and the crossfade signal processing element in the crossfadesignal section, to crossfade to the crossfade signal processing elementhaving the signal processing element as a new characteristic, to performprocessing for replacing any one of the signal processing elements bythe crossfade signal processing element, and to perform the processingon remaining signal processing elements of the plurality of signalprocessing elements in the signal processing section.

(2) The signal processing apparatus according to (1),

wherein the signal processing elements are IIR filters.

(3) The signal processing apparatus according to (2),

wherein the crossfade IIR filters are plural.

(4) The signal processing apparatus according to (2) or (3),

wherein the plurality of IIR filters are connected in series.

(5) The signal processing apparatus according to any one of (2) to (4),

wherein the crossfade signal section includes the crossfade signal IIRfilter, an amplifier, and an adder.

(6) The signal processing apparatus according to any one of (3) to (5),

wherein a number of the plurality of crossfade IIR filters to replaceany one of the plurality of IIR filters can be changed.

(7) The signal processing apparatus according to any one of (2) to (6),

wherein the plurality of IIR filters are connected to amplifiers andadders, respectively, and the crossfade signal section includes thecrossfade IIR filter and the adder.

(8) The signal processing apparatus according to (4),

wherein a bypass amplifier is disposed so as to pass through each IIRfilter and an amplifier at an output side of the IIR filter of theplurality of IIR filters,

a crossfade bypass amplifier is further disposed so as to pass throughthe crossfade signal IIR filter and an amplifier at an output side ofthe crossfade signal IIR filter, and

the control section is configured to control the amplifier and thecrossfade pass amplifier.

(9) The signal processing apparatus according to (2) or (3),

wherein the plurality of IIR filters in the signal processing sectionare connected in parallel, and further a crossfade IIR filter isconnected in parallel.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application JP 2011-266974 filed in theJapan Patent Office on Dec. 6, 2011, the entire contents of which arehereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A signal processing apparatus comprising: acontrol section; a signal processing section connected with a pluralityof signal processing elements and configured to perform signalprocessing for enhancing or attenuating an input signal in a specificfrequency band; and a crossfade signal section including a crossfadesignal processing element capable of replacing at least one of thesignal processing elements among the plurality of signal processingelements, wherein the control section is configured to control any oneof the signal processing elements among the plurality of signalprocessing elements, and the crossfade signal processing element in thecrossfade signal section, to crossfade to the crossfade signalprocessing element having the signal processing element as a newcharacteristic, to perform processing for replacing any one of thesignal processing elements by the crossfade signal processing element,and to perform the processing on remaining signal processing elements ofthe plurality of signal processing elements in the signal processingsection.
 2. The signal processing apparatus according to claim 1,wherein the signal processing elements are IIR filters.
 3. The signalprocessing apparatus according to claim 2, wherein the crossfade IIRfilters are plural.
 4. The signal processing apparatus according toclaim 2, wherein the plurality of IIR filters are connected in series.5. The signal processing apparatus according to claim 2, wherein thecrossfade signal section includes the crossfade signal IIR filter, anamplifier, and an adder.
 6. The signal processing apparatus according toclaim 2, wherein a number of the plurality of crossfade IIR filters toreplace any one of the plurality of IIR filters can be changed.
 7. Thesignal processing apparatus according to claim 2, wherein the pluralityof IIR filters are connected to amplifiers and adders, respectively, andthe crossfade signal section includes the crossfade IIR filter and anadder.
 8. The signal processing apparatus according to claim 4, whereina bypass amplifier is disposed so as to bypass each IIR filter and anamplifier at an output side of the IIR filter of the plurality of IIRfilters, a crossfade bypass amplifier is further disposed so as tobypass the crossfade signal IIR filter and an amplifier at an outputside of the crossfade signal IIR filter, and the control section isconfigured to control the amplifier and the crossfade pass amplifier. 9.The signal processing apparatus according to claim 2, wherein theplurality of IIR filters in the signal processing section are connectedin parallel, and further a crossfade IIR filter is connected inparallel.
 10. A method of processing a signal to change a characteristicof a signal processing apparatus including a control section, a signalprocessing section connected with a plurality of IIR filters andconfigured to perform signal processing for enhancing or attenuating aninput signal in a specific frequency band, and a crossfade signalsection including a crossfade IIR filter capable of replacing at leastone of the IIR filters among the plurality of IIR filters, the methodcomprising: controlling the crossfade IIR filter and changing thecrossfade IIR filter to have a new characteristic; crossfading any oneof the IIR filters among the plurality of IIR filters to the crossfadeIIR filter having the new characteristic; replacing any one of the IIRfilters by the crossfade IIR filter; and enabling to perform thechanging to have a new characteristic, the crossfading, and thereplacing on the plurality of IIR filters.